HOT updates in PostgreSQL for better performance - CYBERTEC
www.cybertec-postgresql.com
HOT updates (Heap Only Tuple) boost PostgreSQL DML performance. This article explains the concept, shows examples and gives tuning advice.

comment_aggregates gets a lot of hammering to set child_count on new replies, it is also probably the 2nd or 3rd largest table in Lemmy’s database, votes for post and comments being the largest